The invention relates to a projection system, such as a liquid crystal display (LCD) projection system, for example.
Referring to FIG. 1, a reflective liquid crystal display (LCD) projection system 5 typically includes an LCD display panel (LCD display panels 22, 24 and 26, as examples) for each primary color that is projected onto a screen 10. In this manner, for a red-green-blue (RGB) color space, the projection system 5 may include an LCD display panel 22 that is associated with the red color band, an LCD display panel 24 that is associated with the green color band and an LCD display panel 26 that is associated with the blue color band. Each of the LCD panels 22, 24 and 26 modulates light from a light source 30 to form red, green and blue images, respectively, that add together to form a composite color image on the screen 10. To accomplish this, each LCD display panel 22, 24 or 26 receives electrical signals that indicate the corresponding modulated beam image to be formed.
More particularly, the projection system 5 may include a beam splitter 14 that directs a substantially collimated white beam 11 of light (provided by the light source 30) to optics that separate the white beam 11 into red 13, blue 17 and green 21 beams. In this manner, the white beam 11 may be directed to a red dichroic mirror 18 that reflects the red beam 13 toward the LCD panel 22 that, in turn, modulates the red beam 13. The blue beam 17 passes through the red dichroic mirror 18 to a blue dichroic mirror 20 that reflects the blue beam 17 toward the LCD display panel 26 for modulation. The green beam 21 passes through the red 18 and blue 20 dichroic mirrors for modulation by the LCD display panel 24.
For reflective LCD display panels, each LCD display panel 22, 26 and 24 modulates the incident beams, and reflects the modulated beams 15, 19 and 23, respectively, so that the modulated beams 15, 19 and 23 return along the paths described above to the beam splitter 14. The beam splitter 14, in turn, directs the modulated beams 15, 19 and 23 through projection optics, such as a lens 12, to form modulated beam images that ideally overlap and combine to form the composite image on the screen 10.
The optical performance of the LCD display panel 22, 24 or 26 may be a function of the temperature of the display panel 22, 24 or 26, and the temperature of the display panel 22, 24 or 26 may rise during operation due to the heating caused by the illumination of the display panels 22, 24 and 26. Thus, the optical performance of the display panels 22, 24 and 26 may also vary during operation. To compensate for thermal drift, the projection system 5 may have a user xe2x80x9ccontrastxe2x80x9d control to adjust the timing of voltages that are applied to the display panels 22, 24 and 26 to form the modulated beam images. However, the temperature of each display panel 22, 24 or 26 may be too high for the timing adjustment to adequately compensate the display panels 22, 24 and 26.
An alternative way to adjust for thermal drift is to apply correcting voltages to drive circuits that form the images on the display panels 22, 24 and 26 in response to a user control. However, unfortunately, this approach may also be ineffective once the temperature of the display panel exceeds an optimal range of temperatures.
Another way to compensate for thermal drift is to lower the temperatures inside the projection system 5, by for example, reducing the heat that is associated with the light beams that illuminate the display panels 22, 24 and 26. However, unfortunately, such techniques may impede the performance of the projection system 5. For example, a dichroic infrared (IR) filter may be used to filter infrared light, a source of heat, from the white beam 11 so that the amount of heat that reaches the display panels 22, 24 and 26 is reduced. However, a dichroic IR filter may have bandstop characteristics which are a function of an angle of incidence of the beam 11, and as a result, the imaging of the beam from the light source 30 may need to be very precise, a condition that may increase the cost of the projection system 5. Furthermore, increasing the accuracy of the imaging of the light source 30 may increase the imaging of defects in the light source 30 itself. Also, to remove enough heat, the IR dichroic filter may have a high bandstop frequency and thus, remove a deep red band of colors from the beam 11. Unfortunately, the removal of the deep red band of colors may degrade the color reproduction accuracy of the system 5.
Thus, there is a continuing need to address one or more of the problems stated above.
In one embodiment of the invention, a projection system includes a light source, a display panel, a temperature gradient panel and a controller. The light source is adapted to generate a first beam of light, and the display panel is adapted to modulate at least a portion of the first beam of light to form an associated modulated beam of light. The temperature gradient panel is thermally coupled to the display panel, and the controller is electrically coupled to the temperature panel and the display panel. The controller is adapted to control the temperature gradient panel to regulate a temperature of the display panel.
In another embodiment, a computer system includes a processor, a display panel, a temperature gradient panel and a controller. The processor is adapted to furnish a first indication of an image. The display panel is adapted to modulate at least a portion of the first beam of light to form an associated modulated beam of light in response to the first indication of the image. The temperature gradient panel is thermally coupled to the display panel, and the controller is electrically coupled to the temperature gradient panel and the display panel. The controller is adapted to control the temperature gradient panel to regulate a temperature of the display panel.
In yet another embodiment, a method includes generating a first beam of light and modulating at least a portion of the first beam of light with a display panel to form an associated modulated beam of light. A temperature gradient is established near the display panel, and the temperature gradient is regulated to control the temperature of the display panel.